Week 5 · Axis 1, Chapter 2 Making a Healthy Body (C) · 3 lessons
2
Pulse before and after exercise
Discover P3 Term 1: Axis 1, Chapter 2
GoalFind a pulse, count it for 15 seconds, multiply by 4, and compare resting and active pulses.
New words
pulse · the beat you can feel where an artery is near the skin, such as the wristheart rate · the number of heartbeats in one minutepredict · to say what you think will happen before you test
Explanation
Each time your heart squeezes, blood pushes against the walls of the tubes and you can feel a little bump called a pulse. Find it on your wrist, below the thumb, with two fingers (not your thumb). A grown-up or a partner watches a timer. Count the beats for 15 seconds. Then multiply by 4 to find the beats in one minute, because 15 seconds is a quarter of a minute. For example, 18 beats in 15 seconds is 18 × 4 = 72 beats in a minute. When we run or jump, our muscles need more oxygen, so the heart beats faster. A quiet game on a screen does not make it beat much faster. Everybody’s pulse is a little different, so there is no good or bad number. Before testing, say your prediction, then check it.
Activity
Beats in 15 s
Beats in 1 min
Sitting
18
18 × 4 = 72
Walking
22
22 × 4 = 88
Jogging in place
30
30 × 4 = 120
Worked examples
Mariam’s partner counts her pulse while she sits still: 20 beats in 15 seconds. 20 × 4 = 80 beats in a minute.
After jogging in place for one minute, a grown-up counts Mariam’s pulse again: 28 beats in 15 seconds. 28 × 4 = 112 beats in a minute. 112 − 80 = 32 more beats than at rest.
Seif predicts: “After a computer game my pulse will be about the same as at rest.” He tests it. Resting: 19 beats in 15 seconds; after the game: 20. His prediction was right.
Class activity
Pulse test, with a partner and a timer. Say your prediction first. 1) Find your pulse. Count 15 seconds sitting. 2) Walk around the room for one minute and count again. 3) Jog gently on the spot for one minute with a grown-up watching, then count again. Multiply each by 4. Stop and rest if you feel dizzy. Draw a bar graph of your three results.
Practice
1
Why do we count the pulse for 15 seconds and multiply by 4?
15 seconds is a quarter of a minute, so 4 quarters make a whole minute.
2
Farida counts 21 beats in 15 seconds. How many beats in a minute?
21 × 4 = 84 beats.
3
Habiba’s resting pulse is 80 beats a minute and after skipping it is 116. How many more beats is that?
116 − 80 = 36 more beats.
4
Why does your heart beat faster when you run?
Your muscles need more oxygen, so the heart pumps blood faster.
